Resonant Electromagnetic Field Research Articles

Prominently enhanced luminescence from a continuous monolayer of transition metal dichalcogenide on all-dielectric metasurfaces

Abstract 2D materials such as transition metal dichalcogenides (TMDCs) are a new class of atomic-layer materials possessing optical and electric properties that significantly depend on the number of layers. Electronic transitions can be manipulated in artificial resonant electromagnetic (EM) fields using metasurfaces and other designed nanostructures. Here, we demonstrate prominently resonant enhancement in the photoluminescence (PL) of atomic monolayer, WS2, doped with a small quantity of Mo. The excitonic PL showed a strong enhancement effect on a higher-order magnetic resonance of all-dielectric metasurfaces consisting of periodic arrays of Si nanopellets. The PL intensity witnessed a 300-fold enhancement compared to the reference PL intensity on a flat silicon dioxide (SiO2) layer, which suggests a drastic change in the dynamics of photoexcited states. Confocal PL microscopy and the analysis revealed that the single photons were coherently emitted from the TMDC monolayer on the metasurface. Furthermore, examining the PL lifetime in the ps and ns timescales clarified two exponential components at the prominent exciton PL: a short-time component decaying in 22 ps and a long-time component lasting over 10 ns. Therefore, we can infer that the radiative components were significantly activated in the TMDC monolayer on the metasurfaces in comparison to the reference monolayer on a flat SiO2 layer.

A Design Strategy for Surface Nanostructures to Realize Sensitive Refractive-Index Optical Sensors.

Refractive-index optical sensors have been extensively studied. Originally, they were surface plasmon resonance sensors using only a flat gold film. Currently, to develop practically useful label-free optical sensors, numerous proposals for refractive index sensors have been made using various nanostructures composed of metals and dielectrics. In this study, we explored a rational design strategy for sensors using surface nanostructures comprising metals or dielectrics. Optical responses, such as reflection and transmission, and resonant electromagnetic fields were computed using a numerical method of rigorous coupled-wave analysis combined with a scattering-matrix algorithm. As a result, good performance that almost reached the physical limit was achieved using a plasmonic surface lattice structure. Furthermore, to precisely trace the refractive-index change, a scheme using two physical quantities, resonant wavelength and reflection amplitude, was found to be valid for a 2D silicon metasurface.

Cascade amplification of optical absorption on III–V semiconductors via plasmon-coupled graphene

Plasmons in graphene (Gr) show many fascinating characteristics, such as dynamic tunability, strong field confinement of light-matter interaction, and highly responsive, which has been widely exploited for a number of applications, including photodetectors, optical modulators, and sensors. In this paper, graphene plasmons (GPs) were motivated by implanting Au nanoparticles (Au NPs) into Ta2O5 thin layers adjacent to the Gr film, and the strong localized surface plasmon resonance (LSPR) effect has been proposed and demonstrated by placing the GPs structure on a III–V semiconductor quantum well saturable absorber (SA). It has been substantiated that the heightened interaction between light and Gr via LSPR predominantly occurs through the mechanisms of resonant energy transfer and local electromagnetic field enhancement, rather than direct electron transfer. Significant improvement on the nonlinear characteristics of the GPs modulated III–V semiconductor SA has been observed with a 17.1% large modulation depth and obviously improved working stability. A 1550 nm passive mode-locked laser has been successfully constructed with a pulse width down to 523 fs by integrating the SA into the laser cavity. This work lays the foundation for the development of high-performance mode-locked lasers and also demonstrates the substantial enhancement of nonlinear optical properties of various materials not limited to III–V semiconductors provided by this GPs' modulated structure; hence, these findings offer extensive prospects for applications in various photonics and optoelectronic devices.

Nonlinear optical response of a strongly-driven quantum dot exciton-biexciton system

We examine the effective linear and the third-order nonlinear optical susceptibilities of an InAs/GaAs semiconductor quantum dot with a cascade exciton-biexciton configuration that is strongly driven by a nearly resonant pump electromagnetic field, while, at the same time, it interacts with a weak electromagnetic field. We assume that the applied fields are linearly polarized, which permits us to simplify the relative energy level diagram by using a three-level ladder-type scheme. We derive the equations of motion, in the dipole approximation, in a rotating frame, and follow an expansion approach to calculate the components of the density matrix which are associated to the effective linear and the self-Kerr third-order nonlinear optical susceptibilities. We present the spectra of the first-order susceptibility and the self-Kerr susceptibility and investigate the dependence of their profiles on the Rabi frequency and the detuning of the pump field, in the one-photon and the two-photon resonance regimes. The role of the biexciton energy shift on the susceptibilities is also studied. In addition, we present a dressed state analysis which appears to be crucial for obtaining a better understanding of several spectral properties of the susceptibilities.

Efficient manipulation of plasmonic modes in single symmetry-breaking Ag nanocube

Efficiently manipulating plasmonic modes by adjusting geometry, spatial arrangement, and the nature of the material has shown great potential in wide applications including ultrasensitive sensing, optical modulation, and surface-enhanced spectroscopy. Symmetry breaking as an effective geometry-controlled method can induce plasmonic hybridization and further tune resonant wavelength, strength, and electromagnetic fields. Herein, through introducing cavity along the cubic lateral edges, we theoretically design symmetry-breaking Ag nanocube that is capable of arbitrarily tuning plasmonic modes based on plasmon hybridization theory. Originated from the hybridization of the nanocube and cavity, bonding and anti-bonding dipole–dipole coupled modes simultaneously exhibit trends of blueshifts and redshifts by decreasing the overlapped domain and by increasing the radius of cavity. Moreover, the hybrid modes can be independently tuned by changing the edge length of the cube and the number and the location of cavity. These findings not only advance the understanding of the mechanism of light-matter interactions in symmetry-breaking Ag nanocube but also provide further guidance for designing efficient nanophotonic platforms in plasmon-enhanced spectroscopy and optical wave manipulations.

Microwave cavity resonator sensor with an octagonal cross section for thickness measurement of coatings on carbon fibre composites

Manual painting is commonly conducted on an aircraft's exterior, and the coating thickness should be within the allowable range. For quality control, the thickness requires accurate assessment. However, the current non-destructive testing techniques for metallic substrates cannot be well suited to the widely used carbon fibre-reinforced polymer composites, which are less conductive. Here we present a new microwave cavity resonator sensor, in which an octagonal cross section (an intermediate shape between a cylinder and a sphere) is adopted to easily eliminate mode degeneracy. A design strategy incorporating electromagnetic simulation is presented, and an accurate model is developed for the extraction of the resonance frequency and quality factor from the asymmetrical responses. In the tests, the open cavity is placed on a composite sample, and coating thickness change causes cavity wall impedance perturbation, leading to resonance frequency shift. From the experiments, a linear relationship is seen between the coating thickness difference and resonance frequency shift, thereby facilitating the estimation process. As the resonant electromagnetic fields are similar to those of the cylindrical TE011 mode, insensitivity to the conductivity and anisotropy of the composite is also demonstrated, enabling convenient implementation. Reasonable accuracy is obtained for thicknesses up to 2 mm. In the prediction of two- and multi-layered coating cases, errors within ±5% are obtained. The sensor developed offers efficient on-site measurement of paint coatings on carbon fibre composite structures.

Effective two-level approximation of a multilevel system driven by coherent and incoherent fields

The numerical simulation of multiple scattering in dense ensembles is the mostly adopted solution to predict their complex optical response. While the scalar- and vectorial-light-mediated interactions are accurately taken into account, the computational complexity still limits current simulations to the low saturation regime and ignores the internal structure of atoms. Here, we propose to go beyond these restrictions, at constant computational cost, by describing a multilevel system by an effective two-level system that best reproduces the coherent and total scattering properties in any saturation regime. The correspondence of our model is evaluated for different experimentally realistic conditions such as the modification of the driving field polarization, the presence of stray magnetic fields, or an incoherent resonant electromagnetic field background. The trust interval of the model is quantified for the ${\mathrm{D}}_{2}$ line of $^{87}\mathrm{Rb}$ atoms, but it could be generalized to any closed transition of a multilevel quantum system.

RADAR TECHNIQUE FOR AIRCRAFT WITH AN ARTIFICIALLY REDUCED RCS UNDER CONDITIONS OF APPLICATION A RESONANT ELECTROMAGNETIC FIELD

The paper presents the results of a study of the radar technique for aircraft with an artificially reduced radar cross section (RCS) under the condition of using a resonant electromagnetic field. It is shown that the detection and tracking of air objects under conditions of artificially reduced RCS is carried out using radar information with resonant excitation of their radar absorbing coating. It is proposed to carry out tracking and detection of aircraft by a complex combination of an active radar channel with the formation of a resonant radio signal and a passive radar capable of receiving signals formed by an excited surface. It has been determined that by increasing the power level of the irradiating signal to 20-30%, it is possible to increase the area of the local conduction region of the dielectric by 10 times, which means that it will simplify the technical implementation of the method of locating aircraft. The proposed control methods make it possible to provide the necessary probability of detection accompanied by a radar target in a difficult jamming environment and thus increase the potential capabilities of the radar. In the course of the study, it was determined that the excitation and heating of the coating during enthalpy directly depends on the energy flux density of the electromagnetic microwave field per unit mass and area of the substance. It has been established that purposeful control of this effect makes it possible to substantiate the possibility of using enthalpy as a factor in excitation of air target coatings with an artificially reduced reflection area (RCS). The conditions for increasing the efficiency of radar targets with an artificially reduced RCS using a concentrated resonant electromagnetic field have been clarified. It is determined that the influence of such a field is accompanied by the concentration of the energy of the electromagnetic field in the crystal structure of the radio-absorbing coating of the aircraft due to the resonant irradiating signal, which causes temporary local conductivity and thermal radiation. Calculations of quantitative indicators characterizing the possibility of changing the electrically conductive properties of a carbon-type dielectric at a distance for the practical application of advanced radar systems are presented.

Quantum theory of two-dimensional materials coupled to electromagnetic resonators

We present a microscopic quantum theory of light-matter interaction in pristine sheets of two-dimensional semiconductors coupled to localized electromagnetic resonators such as optical nanocavities or plasmonic particles. The light-matter interaction breaks the translation symmetry of excitons in the two-dimensional lattice, and we find that this symmetry-breaking interaction leads to the formation of a localized exciton state, which mimics the spatial distribution of the electromagnetic field of the resonator. The localized exciton state is in turn coupled to an environment of residual exciton states. We quantify the influence of the environment and find that it is most pronounced for small lateral confinement length scales of the electromagnetic field in the resonator, and that environmental effects can be neglected if this length scale is sufficiently large. The microscopic theory provides a physically appealing derivation of the coupled-oscillator models widely used to model experiments on these types of systems, in which all observable quantities are directly derived from the material parameters and the properties of the resonant electromagnetic field. As a consistency check, we show that the theory recovers the results of semiclassical electromagnetic calculations and experimental measurements of the excitonic dielectric response in the linear excitation limit. The theory, however, is not limited to linear response, and in general describes nonlinear exciton-exciton interactions in the localized exciton state, thereby providing a powerful means of investigating the nonlinear optical response of such systems.

Simulation of Earth‐Ionosphere Cavity Resonances With Lightning Flashes Reported by OTD/LIS

AbstractLightning flashes cause a globally resonant electromagnetic wave field known as Earth‐ionosphere cavity resonances. This global wave field is simulated here by use of lightning flashes reported by the lightning imagers on board the Optical Transient Detector (OTD)/Lightning Imaging Sensor (LIS) space missions. The stochastic occurrence of global lightning flashes in time and space is described with a likelihood function composed of a series of delta functions. This likelihood function is generated by random variates calculated from inverse transform sampling of the global lightning distributions measured by OTD/LIS. The simulation uses spherical harmonic expansion coefficients, calculated from frequency and distance dependent magnetic field measurements, to describe the wave field around the Earth. The incoherent superposition of the waves at each location results in simulated time series and spectra. The simulations agree very well with actual measurements of magnetic fields with a radiometer at Arrival Heights in the Antarctic as part of the Stanford ELF/VLF Radio Noise Survey. The simulated relative radiant energy distributions are attributed to corresponding “Earth‐ionosphere cavity brightness temperatures” TEIC. The spherical harmonic expansion of these brightness temperatures exhibits a spectrum where the amplitudes of the spatial expansion coefficients decrease with increasing angular degree. The calculated Earth‐ionosphere cavity brightness temperatures can be used for comparison with atmospheric temperatures in future studies.

Transverse magnetic modes of localized spoof surface plasmons

Electric and magnetic modes establish the basis of the localized spoof surface plasmons (LSSPs), both of which are transverse electric (TE) modes. In this paper, the concept of transverse magnetic (TM) modes of LSSPs is proposed, and the double-layer planar-circular-grating resonator is demonstrated to support the TM modes in addition to the TE modes. In numerical simulations, the TE and TM modes were excited by a plane wave and an aperture, respectively, and their resonant frequencies and electromagnetic field distributions were demonstrated to be different. The electric field of the TE mode is parallel to the grating, while the magnetic field of the TM mode is parallel to the grating. In experiments, multiple TE and TM LSSPs modes were excited by a magnetic coupler. The magnetic coupler can be rotated to distinguish the TM modes from the TE ones, which provides conclusive evidence of the existence of the TM modes. Compared with the TE LSSPs modes, the TM LSSPs modes have the advantages of high sensitivity to the distance between layers and high quality factors (Q-factors), which hold promise for providing improvements on compact applications of LSSPs. Based on the proposed concept, therefore, the classification standard of the LSSPs is expanded to make it more scientific and comprehensive.

Ridge Gap Waveguide based band pass filter for Ku-band Application

This paper describes a simple, low loss, compact tuneable band pass filter based on ridge gap waveguide (RGW) technology for the Ku-band applications. This is achieved by keeping the height of the air gap in the gap guide structure equal to the thickness of the substrate or base of the structure. The resonant frequency and electromagnetic (EM) field distribution of the structure is investigated. This filter is designed by inserting the proposed ridge in the cut-off region of the gap waveguide. The frequency of tuning has been carried out using the slot created on ridge, which generates capacitive effect. Experimental results of the manufactured structure show an insertion loss of approximately 0.15 dB and a return loss of 16.38 dB over 4.5% relative bandwidth in Ku-band. The structure, put forwarded here, has been designed and optimized in the CST microwave studio environment and simulated results are validated by experimental results. The size of the structure is 64.65 mm × 64.65 mm × 7 mm.

Effects of Resonant Electromagnetic Fields on Biofilm Formation in Pseudomonas aeruginosa

The global rise of antimicrobial resistance (AMR) constitutes a future health threat and dictates a need to explore alternative and non-chemical approaches. The aim of this study was to explore the use of weak resonant electromagnetic fields as a method to disrupt biofilm formation of a pathogenic bacterium in cystic fibrosis patients. We developed a bioresonance laboratory setup able to distinguish between changes in planktonic growth and changes in biofilm formation and showed that certain resonant frequencies were able to affect biofilm formation without affecting planktonic growth. In addition, we show that the ambient day-to-day magnetic field affects biofilm formation in a non-consistent manner. Overall, we conclude that our assay is suitable for studying the potential of resonant magnetic fields as a treatment and prevention strategy to prevent biofilm infections, and that certain resonant frequencies may be used as future medical applications to combat antimicrobial resistance.

Manipulating valley-polarized photoluminescence of MoS2 monolayer at off resonance wavelength with a double-resonance strategy

The intrinsic spin-valleys in monolayer transition metal dichalcogenides make them promising for exploring new-generation valleytronic and spintronic devices. However, it is very challenging to detect and manipulate a specific valley with off resonance electromagnetic fields at room temperature due to their ultrashort lifetimes and phonon-assisted intervalley scattering. Here, utilizing the sputtering and the focused ion beam milling methods, we fabricate a quasi-three-dimensional chiral microstructure using molybdenum disulfide. Based on chirality and double plasmonic resonances, we realize off resonance wavelength control of valley-polarized photoluminescence at room temperature. Furthermore, we find that the chiral field excitation enhancement (13) and chiral quantum yield amplification (1.35 times) contribute to the huge differences in the photoluminescence of valleys. These results reported here may pave the way for further development of on-chip photonic integration of two-dimensional materials.

Research Advance on the Sensing Characteristics of Refractive Index Sensors Based on Electromagnetic Metamaterials

Among different sensing platforms, metamaterials composed of subwavelength or deep subwavelength sized metal resonance elements arrays that are etched on semiconductor substrates or dielectric substrates exhibit excellent characteristics due to the strong localization and enhancement of resonance electromagnetic fields. As a new type of detection method, metamaterial sensors can break through the resolution limit of traditional sensors for a small amount of substance and have the advantages of high sensitivity, fast response, and simple measurement. Significant enhancement of the sensing characteristics of metamaterial sensors was realized by optimizing microstructures (single split-ring, double split-ring, nested split-ring, asymmetric split-ring, three-dimensional split-ring, etc.), using ultrathin substrates or low-index substrate materials, etching away local substrate, and integrating microfluidic channel, etc. This paper mainly reviews the research advance on the improvement of sensing characteristics from optimizing resonance structures and changing substrate materials and morphology. Furthermore, the sensing mechanism and main characteristic parameters of metamaterial sensors are introduced in detail, and the development trend and challenge of metamaterial sensing applications are prospected. It is believed that metamaterial sensors will have potential broader application prospects in environmental monitoring, food safety control, and biosensing in the future.

Enhanced Dipole Antenna for RFID by Using Metamaterials

The paper at hand discusses a novel method of miniaturization of antenna design using metamaterials. We suggest a novel method to improve frequency characteristics while reducing antenna size. This method is based on the connection of this element resonant two split rings resonator. The resonant frequency, return loss, bandwidth, radiation pattern, gain, directivity, electromagnetic field, and current supplied by the proposed antenna are the parameters addressed in this study. CST software generates all simulation results.

Coherent cyclotron emission with a helical wavefront from multi-electron system accelerated by the circularly polarized wave

In this study, we calculated coherent electron cyclotron emission (ECE) with helical wavefront from a multi-electron system which passes through a magnetic mirror field with cyclotron motion. ECE from a multi-electron system is usually incoherent radiation due to the random rotation phase of each electron, and it is difficult to observe the helical wavefront. However, when a resonant external electromagnetic field is applied, the gyro-phase of electrons are controlled, and coherent ECE is expected to be observed. These processes were numerically calculated under the given experimental condition and confirmed that the higher harmonics ECE has helical wavefront.

Refractive index sensing characteristics of electromagnetic metamaterial absorber in terahertz band

<sec>Terahertz metamaterial (THz MM) absorber, as an important type of MM functional device, can not only achieve perfect absorption of incident THz waves, but also act as a refractive index sensor to capture and monitor changes in the information about surrounding environment. Generally, the sensing characteristics of the THz MM absorber can be improved by optimizing the structure of the surface metal resonance unit and changing the material and shape of the dielectric layer. In order to further study the influence of the intermediate dielectric layer on the sensing characteristics of the THz MM absorber, in this paper we implement three THz MM absorbers with continuous dielectric layer, discontinuous dielectric layer and microcavity structure based on the metallic split-ring resonator array, and conduct in-depth study of their sensing characteristics and sensing mechanism. </sec><sec>The THz MM absorber with continuous dielectric layer and metallic split-ring resonator array can be used as a refractive index sensor to realize the sensing detection of analytes coated on its surface with different refractive indexes. However, it can be seen from its corresponding refractive index frequency sensitivity and FOM value that the detection sensitivity of this sensor is limited, and its sensing performance still needs improving. The main reason is that most of the resonant electromagnetic (EM) field of the THz MM absorber is tightly bound in the intermediate dielectric layer, and only the fringe field extending to the surface of the MM absorber resonant unit array can interact with the analyte to be measured, and the intensity of this part of the field directly determines the sensitivity of the sensor. In order to further improve the refractive index frequency sensitivity of the THz MM absorber, reduce the restriction of the intermediate dielectric layer to the resonant EM field, and enhance the interaction between the resonant EM field and the analyte to be measured, a THz MM absorber with discontinuous dielectric layer is proposed and studied. Compared with the THz MM absorber with continuous dielectric layer, the THz MM absorber based on discontinuous dielectric layer can be used as a refractive index sensor to realize higher-sensitivity sensing and detection of the analyte coated on the surface. In order to further enhance the interaction between the resonant EM field and the analyte to be measured, and improve the refractive index frequency sensitivity of the THz MM absorber, a THz MM absorber with a microcavity structure is proposed. For this THz MM absorber, the analyte to be measured filled in the microcavity structure can serve as the intermediate dielectric layer of the THz MM absorber, and when the metallic split-ring resonator array is completely immersed in the analyte to be measured, the resonant EM field originally confined in the intermediate dielectric layer and the analyte to be measured completely overlap in space. Therefore, compared with the first two THz MM absorbers, THz MM absorber with a microcavity structure achieves the tightly and fully contacting the resonant EM field, thereby greatly improving its sensitivity as a sensor. </sec><sec>The results show that in order to improve the sensing characteristics of the THz MM absorber, such as the refractive index sensitivity and the maximum detection range, in addition to using the materials with lower relatively permittivity as the intermediate dielectric layer, the morphology of the intermediate dielectric layer can be changed, thereby reducing the restraint of the intermediate dielectric layer on the resonant field and enhancing the coupling between the resonant field and the analyte to be measured. Compared with the conventional THz MM absorber with continuous dielectric layer, the MM absorber with discontinuous dielectric layer and microcavity structure have many superior sensing characteristics, and can be applied to the high-sensitivity and rapid detection of analytes to be measured, and has a broader application prospect in the future sensing field. </sec>

Applying Resonant Electromagnetic Fields in Membrane Channels of Tumor Cells: The Future of Cancer Treatment

Emanuele Calabrò1,5* and Salvatore Magazù1-5 Author Affiliations 1Department of Mathematical and Informatics Sciences, Physical Sciences and Earth Sciences of Messina University, Viale Ferdinando Stagno D’ Alcontres 31, Italy 2Le Studium, Loire Valley Institute for Advanced Studies, Orléans & Tours, France 3Centre de Biophysique Moleculaire Laboratoire Interfaces, Confinement, Matériaux et Nanostructures (ICMN, France 4Istituto Nazionale di Alta Matematica “F. Severi” – INDAM - Gruppo Nazionale per la Fisica Matematica – GNFM 5CISFA “Interuniversity Consortium of Applied Physical Sciences” (Consorzio Interuniversitario di Scienze Fisiche, Italy Received: October 23, 2020 | Published: November 06, 2020 Corresponding author: Emanuele Calabrò, Department of Mathematical and Informatics Sciences, Physical Sciences and Earth Sciences of Messina University, Italy DOI: 10.26717/BJSTR.2020.31.005142

A feasibility study of a real‐time visualization method for electromagnetic fields

AbstractWe present a feasibility study of a real‐time visualization method for electromagnetic fields. When a resonant laser is used to irradiate gaseous atoms enclosed in a glass cell, the atoms absorb the light and immediately radiate as fluorescence. If a resonant laser and electromagnetic field are used to irradiate the gaseous atoms simultaneously, fluorescence of the light is stronger. The difference between the strength values of fluorescence of light can be used for electromagnetic field visualization. We succeeded in demonstrating a real‐time visualization of electromagnetic fields radiated from a horn antenna and an aperture of a waveguide in free space.